The possible collision supports the contention of driver William Scott of Mullen Trucking, who was hauling the well casing south from Canada, that he felt squeezed by the passing truck and kept to the right — where the curved crossbeams turned out to be lower than Scott’s load.

Scott’s cargo, 15 feet 11 inches tall, hit beams that were only 15 feet 5 inches above the pavement on the right side.

Investigators are also sorting through conflicting information about whether the warning pole on a pilot car struck the bridge, signaling the load might not fit. Scott says he didn’t see unusual motion in the pole, but a nearby motorist, Dale Ogden, said the pole hit four or five crossbeams.

The bridge failure at 7 p.m. on May 23, 2013, severed part of a freeway where 71,000 vehicles a day cross the river. Two cars plunged into the river during the collapse, but the three people in them escaped serious injury.

The Washington State Department of Transportation (WSDOT) replaced the downed steel-truss section, one of four spans, with a deck supported from beneath by concrete girders.

WSDOT also replaced curved crossbeams on the remaining three spans with straight beams, to allow uniform 18-foot clearance.

The NTSB’s findings about what caused the collapse will be published in a few weeks.

Some highlights from 2,000 pages of documents released Wednesday:

•Scott carries mostly oversize loads, and said his last trip south on I-5 was two years earlier. He worried about clearances, avoiding two overpasses near Chilliwack, B.C., by using off­ramps. With a Washington-based pilot-car driver, he checked his documents and measurements at the border, and a weigh station in Skagit County.

According to Scott, the pilot car and his truck were “where we were supposed to be” as they approached the bridge. Then another truck, “came up very fast on the left — in the left lane — and squeezed me.”

That’s when his load struck the crossbeams, which are connected to other beams supporting the span.

“I can’t say what happened because I had never been in the cab when something like that happened,” he said. “So it was just a horrendous boom and things were — it was violent in the cab … I’m not a messy guy, but my stuff was everywhere in there.”

• The passing trucker, Amandeep Sidhu, said he saw no evidence the high load’s driver was signaling or trying to move left. Sidhu passed at 62 or 63 mph, on the bridge.

A State Patrol detective asked if Sidhu felt a sideswipe collision, but he said no. He said he thought a loud crack was the well casing on the other truck bouncing on the flatbed — instead of the bridge being fractured. He said he learned of the collapse later, at a fueling station near Arlington.

• The pilot-car driver, Tammy DeTray of Olympic Peninsula Pilot Service, has more than 20 years’ experience. She told investigators her pole didn’t strike any beams. DeTray was in the midst of a six-minute, hands-free cellphone call, the NTSB records say.

She told investigators she was speaking with her husband, who holds a commercial driving license, about clearance hazards south on I-405. She had measured the pole repeatedly at 16 feet, 2 inches; state troopers measured it at 16 feet even.

For several months after the collapse, the 1955-vintage Skagit River Bridge served as a symbol of the nation’s crumbling infrastructure, though it was neither proposed for replacement nor classified as deficient. But it is “fracture-critical,” which means an impact to one beam can cripple an entire span.